Shovels of the aforementioned type are constructed as convertible attachments for excavators, wheel loaders or corresponding working implements and have two steel side walls, which are substantially parallel and reciprocally spaced from one another. A steel shovel bottom extends between the side walls, with the steel shovel bottom interconnecting the side walls at one end thereof and defining at least one open side, thereby forming a skip-like shovel.
Conventionally, a wedge-shaped pickup ledge is provided on the lower edge of the shovel bottom, with the ledge having teeth for facilitating a penetration of the shovel into the soil or material to be picked up. The teeth and optionally also the ledge are made from hardened wear-resistant steel and, when the teeth and/or the ledge become worn, they are replaced or repaired by deposit welding. Shovels of this type are also referred to a loading shovels. They are also so-called hinged shovels, which comprise two shovels corresponding in a draw-like manner and which fundamentally have the same construction as a loading shovel and, the subject matter of the present invention is directed to both types of shovels.
The shovel is, for example, fitted to the free end of an excavator shaft and connected to the hydraulic circuit of the excavator, so that the shovel can be pivoted together with the cantilever arm and the excavator shaft and is also adjustable relative to the shaft. The shovel is normally used for digging out pits and trenches, for moving and taking up dumped material and also for loading vehicles with loose material or displacing the latter.
Recently such shovels have been increasingly used for working up natural or artificial raw and building materials, i.e. for recycling. For example, specific reference is made here to the recovery of concrete building materials. On removing or demolishing concrete structures or components generally relatively large fragments are formed, which are too large and heavy to be reused in a simple manner. Therefore the concrete fragments are directly crushed with the demolition apparatus or in separate crushing plants to a size such that they can be given an appropriate reuse function, dependent on the nature and characteristics of the concrete.
For transporting and loading, as well as for transporting the demolished material to the crushing plant, use is normally made of earthmoving equipment such as excavators, wheel loaders, etc., which are provided with a loading shovel of the aforementioned type. The demolition material taken up in this way comprises, apart from relatively large fragments which are still to be crushed, pieces of concrete which already have such a limited size that further crushing in the crushing plant is not needed and may not in any case be possible. If these small concrete fragments are still supplied to the crushing plant, its remaining capacity for large fragments to be crushed is reduced. Therefore the operating efficiency of the crushing plant, i.e. the quantity of crushed material per unit of time is reduced. In fact, material of very small particle size is highly undesirable in crushing plants, because the small particle size leads to increased wear to the crushing tools and to other malfunctions.
It is therefore appropriate to carry out a presorting of the demolition material before it is supplied to the crushing plant. This could take place by a known shovel having in one or more slits on the bottom thereof and which is, in particular, used for separating solids and liquids. Although such a slit arrangement is adequate for the screening action when separating a liquid from a solid, e.g. for draining soil taken up with the shovel when digging pits or when excavating underwater, but it has been found that demolition material cannot be sorted with such a shovel, because the concrete fragments frequently build up in front of the slits or are jammed in the latter, so that the slits lose their sorting action. In this way more small material is held back in the shovel without the desired screening or sorting action occurring and the material then undesirably passes into the crushing plant.
In order to avoid the aforementioned disadvantages, an attempt has been made to use a convertible attachment in the form of a rotary drum, i.e. a revolving screen. The latter has a closable opening, which can be used for taking up the material to be sorted. After closing the opening the drum is vibrated, so that the material contained therein is presorted or screened out, accompanied by a constant revolution action. However, such a revolving screen is not only constructionally very complicated and therefore expensive, but the sorting of the material is time and therefore cost-intensive. It is also not possible to use the drum for other purposes, e.g. for loading "screenings".